//functions.js
//Create a boolean variable to check for a valid IE instance.
var xmlhttp = false;
//Check if we are using IE.
try {
//If the javascript version is greater than 5.
    xmlhttp = new ActiveXObject("Msxml2.XMLHTTP");
} catch (e) {
//If not, then use the older active x object.
    try {
//If we are using IE.
        xmlhttp = new ActiveXObject("Microsoft.XMLHTTP");
    } catch (E) {
//Else we must be using a non-IE browser.
        xmlhttp = false;
    }
}

//If we are using a non-IE browser, create a JavaScript instance of the object.
if (!xmlhttp && typeof XMLHttpRequest != 'undefined') {
    xmlhttp = new XMLHttpRequest();
}
//A variable used to distinguish whether to open or close the calendar.
var showCalendar = true;

function showHideCalendar() {
    //The location we are loading the page into.
    var objID = "calendar";
    //Change the current image of the minus or plus.
    if (showCalendar == true) {
        //Show the calendar.
        document.getElementById("opencloseimg").src = "images/mins.gif";
        //The page we are loading.
        var serverPage = "calendar.php";
        //Set the open close tracker variable.
        showCalendar = false;
        var obj = document.getElementById(objID);
        xmlhttp.open("GET", serverPage);
        xmlhttp.onreadystatechange = function () {
            if (xmlhttp.readyState == 4 && xmlhttp.status == 200) {
                obj.innerHTML = xmlhttp.responseText;
            }
        }
        xmlhttp.send(null);
    } else {
        //Hide the calendar.
        document.getElementById("opencloseimg").src = "images/plus.gif";
        showCalendar = true;
        document.getElementById(objID).innerHTML = "";
    }
}
